The present invention generally relates to the field of commercial cooking devices, and more particularly to gas burners for commercial cooking devices with increased performance.
A wide variety of gas burners have been used over the years in commercial cooking devices (e.g., commercial stoves, boilers, and the like). One common approach is to supply natural gas to the burner at a pressure regulated down to a pressure of 4-8 inches of water, mix the natural gas with ambient air (primary air) at an upstream portion of the burner, and then route the gas/air mixture to a plurality of downstream burner ports for combustion. For some burner designs, proper combustion also requires additional air, referred to as secondary air, to be supplied to the combustion site from a path external to the burner; other burner designs do not require this secondary air.
One important aspect of gas burners is their ability to efficiently convert the chemical potential energy of the gas into useful heat through the combustion process. It has long been known that the proper mixing of air and gas prior to the ejection of the same from the burner ports is very important in achieving good combustion. If not enough/too much air is provided, then the combustion process is less efficient, resulting in wasted energy and/or increased cooking times. However, the control of the mixing process is viewed in the art as being rather unpredictable, particularly in the wide variety of circumstances encountered in real world installations. Typically, a single venturi is used to mix the primary air with the incoming gas. Frequently, a mechanism is provided just upstream of the venturi to allow the operator to manually adjust the airflow for optimum combustion, such as by providing a variable shutter arrangement at the ambient air inlet. However, this has proved less than ideal in practice, given the myriad of other items vying for the operator""s attention in the real world. In addition, such single venturi burners are typically limited as to their maximum heat output. Another approach is supply the burner with a preset mixture of air/gas from a canister, rather than relying on on-location mixing with ambient air. However, reliance on premix canisters is both cumbersome and frequently cost prohibitive.
Therefore, there remains a need for alternative burner designs, particularly alternative burner designs that are efficient and/or are able to produce more useful heat from a readily available gas supply.
The present invention is directed to an improved gas burner design and a method of operating the same. The burner of the present invention utilizes a unique approach for combining the gas and ambient air on-site to produce a more efficient and/or more productive combustion process. To do so, the present invention forces a premixing of the incoming gas with ambient air by moving the front face of the gas orifice upstream from the normal location and spacing it from the front face of the venturi portion of the burner. The air used for the premixing is pulled through this gap and enters the venturi section with the gas. Additional ambient air, the primary air, flows into the venturi via separate openings spaced from the gas/premix air opening, and then combines therewith in the venturi.
In one embodiment, the burner has a main burner body with a plurality of output ports towards one end and an opposing input end, with the venturi therebetween. A central opening is disposed on the upstream side of the venturi. The gas orifice outputs gas at a front face disposed upstream and spaced from this central opening. In addition, other opening(s), called the primary opening(s), are disposed on the upstream side of the venturi and spaced from the central opening. The primary mixing air flows through these primary opening(s) and combines with the gas in the venturi. Both the gas and the premix air flow through the central opening and the premix air at least partially combines with the gas before the primary air combines with the gas. The combination of the gas, the premix air, and the primary air the routed to the output ports for combustion. The central opening and the primary openings may advantageously be provided by a restricting plate rotatably moveable with respect to the input end. A mounting bracket may be connected to the restricting plate to support the gas orifice body in spaced relation to the central opening. Such a burner combusts the gas with an efficiency factor of at least 45, and optionally at a rate of xe2x89xa730,000 Btu/hr. In some embodiments, the burner combusts the gas at a rate of approximately 40,000 Btu/hr with an efficiency factor of at least 50.